Acrylic acid modified polyester resin as well as preparation method and application thereof

Abstract

The invention discloses acrylic acid modified polyester resin as well as a preparation method and application thereof. The acrylic acid modified polyester resin is prepared from the following preparation raw materials: polyol, polyacid, acrylic resin, an acidolysis agent and an esterification catalyst, the mass percent of the acrylic resin in the preparation raw materials of the acrylic modified polyester resin is 3-13%; the acrylic resin is prepared from the following preparation raw materials in parts by mass: a hard monomer, a soft monomer, a reactive monomer, a solvent and an initiator; the mass percent of the reactive monomer in the preparation raw materials of the acrylic resin is 6-12%; the reactive monomer comprises at least one of methacrylic acid, acrylic acid, hydroxyethyl acrylate or glycidyl methacrylate. By regulating and controlling the specific raw material composition of the acrylic resin, the obtained polyacrylic resin has good weather resistance, and the finally formed acrylic acid modified polyester resin can be collinearly produced and coated with the existing polyester resin.

Description

Technical Field

[0001] This invention belongs to the field of polymer technology, and particularly relates to an acrylic-modified polyester resin, its preparation method, and its application. Background Technology

[0002] Polyester resin is a type of high molecular weight polymer formed by catalytic esterification and vacuum polycondensation of polybasic acids and polyols as monomers. Due to its excellent comprehensive performance, relatively low cost, and safety and environmental friendliness, polyester resin for powder coatings is widely used in architectural aluminum profiles, home appliances, and automotive parts. However, due to the limitations of its composition and structure, aging is one of the major challenges facing polyester resin, especially in applications such as industrial roll materials, automotive parts, and waterproofing materials. During use, polyester resin is prone to irreversible aging reactions such as hydrolysis, thermo-oxidative degradation, and ultraviolet-induced oxidative degradation, leading to a significant reduction in its durability.

[0003] Acrylic resin is a resin copolymerized from (meth)acrylates and other olefin monomers. Acrylic resin for powder coatings is a coating material that has developed rapidly in recent years. It has excellent weather resistance and is suitable for long-term outdoor use. Its weather resistance is far superior to that of polyester resin. However, there are certain limitations in the application of acrylic resin: 1) Due to the poor compatibility between acrylic resin and polyester resin, they usually cannot be produced on the same production line as polyester resin in powder coating production and application; 2) Compared with polyester resin, acrylic resin is more brittle and has relatively poor impact resistance and flexibility.

[0004] Existing technology discloses a method for preparing polyester-grafted polyacrylate polymers for transparent powder coatings. The resin used is polyester-grafted polyacrylate, primarily to improve the leveling, clarity, and high humidity and heat resistance of the transparent powder coating, without addressing the improvement of the polyester resin's weather resistance. Furthermore, studies have reported that fluorocarbon resins possess extremely excellent weather resistance, showing no significant change in appearance after more than 20 years of outdoor use, and exhibiting excellent chemical resistance, temperature resistance, and impermeability. However, they are expensive, and their poor pigment wetting and dispersibility leads to lower gloss. More seriously, perfluoroalkyl and polyfluoroalkyl substances are harmful to the environment and human health, thus their use is restricted.

[0005] Powder coatings have developed rapidly in recent years, and their preparation process has become relatively mature. However, traditional ultra-weather-resistant polyester resins can no longer fully meet the market's demand for weather resistance. Summary of the Invention

[0006] In order to overcome at least one of the problems existing in the prior art, one of the objectives of the present invention is to provide an acrylic modified polyester resin that can effectively improve the weather resistance of polyester resin and can be produced and coated on the same production line as polyester resin.

[0007] The second objective of this invention is to provide a method for preparing the above-mentioned acrylic modified polyester resin.

[0008] The third objective of this invention is to provide a powder coating.

[0009] The fourth objective of this invention is to provide a coating.

[0010] The fifth objective of this invention is to provide an application of the above-mentioned acrylic modified polyester resin, or the above-mentioned powder coating, or the above-mentioned coating.

[0011] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A first aspect of the present invention provides an acrylic-modified polyester resin, wherein the acrylic-modified polyester resin is prepared from raw materials comprising the following parts by weight: 31-40 parts of polyol, 31-60 parts of polyacid, 4-30 parts of acrylic resin, 5-20 parts of acid hydrolysate and 0.01-0.2 parts of esterification catalyst; wherein the acrylic resin comprises 3-13% by weight of the raw materials for preparing the acrylic-modified polyester resin; The acrylic resin is prepared from the following raw materials in parts by weight: 40-70 parts hard monomer, 5-20 parts soft monomer, 5-15 parts reactive monomer, 18-50 parts solvent and 0-5 parts initiator; the reactive monomer is 6-12% by weight in the raw materials for preparing the acrylic resin; the reactive monomer includes at least one of methacrylic acid, acrylic acid, hydroxyethyl acrylate or glycidyl methacrylate.

[0012] In this invention, hard monomers are one of the main raw materials for acrylic resin, accounting for more than 40% of the total mass of raw materials for preparing acrylic resin. For example, it can be any value of 40%, 50%, 60% or 70% or any range between two.

[0013] In this invention, polyol is one of the main raw materials for acrylic modified polyester resin, accounting for more than 31% of the total mass of raw materials for preparing acrylic modified polyester resin, for example, any value of 31%, 35% or 40% or any range between two.

[0014] Preferably, the reactive monomer is selected from one of the following combinations: 1) 10-25 parts by weight of methacrylic acid and 75-90 parts by weight of acrylic acid; or 2) hydroxyethyl acrylate; or 3) glycidyl methacrylate.

[0015] More preferably, the reactive monomer is selected from glycidyl methacrylate.

[0016] Preferably, the reactive monomer is 6.5-10% by mass in the raw materials for preparing the acrylic resin; more preferably, it is 7-9%.

[0017] By adjusting the type and amount of reactive monomers, the resulting polyacrylic acid resin has better weather resistance and better compatibility with polyester resin.

[0018] Preferably, the hard monomer includes at least one of methyl methacrylate, methyl acrylate, styrene, or cyclohexyl methacrylate.

[0019] More preferably, the hard monomer is selected from one of the following combinations: 1) 35-70 parts by weight of methyl methacrylate, 5-20 parts by weight of methyl acrylate and 5-2 parts by weight of cyclohexyl methacrylate; or 2) 35-70 parts by weight of methyl methacrylate, 5-20 parts by weight of methyl acrylate and 10-45 parts by weight of styrene.

[0020] More preferably, the hard monomer is selected from the following combination: 35-70 parts by weight of methyl methacrylate, 5-20 parts by weight of methyl acrylate and 5-2 parts by weight of cyclohexyl methacrylate.

[0021] Preferably, the soft monomer includes at least one of n-butyl acrylate, n-hexyl acrylate, dodecyl acrylate, or lauryl acrylate.

[0022] More preferably, the soft monomer is selected from the following combination: 1 to 20 parts by mass of n-butyl acrylate, 1 to 10 parts by mass of n-hexyl acrylate and 75 to 100 parts by mass of lauryl acrylate.

[0023] By further selecting the above-mentioned reactive monomers, hard monomers, or soft monomers, the resulting acrylic resin can have better weather resistance and good compatibility with conventional polyester resins, enabling the final acrylic-modified polyester resin to be produced and coated on the same production line as existing polyester resins.

[0024] Preferably, the solvent includes at least one selected from ethyl acetate, butyl acetate, n-butanol, xylene, propylene glycol methyl ether acetate, ethylene glycol monomethyl ether, or ethylene glycol monobutyl ether.

[0025] More preferably, the solvent includes at least one of ethyl acetate, n-butanol, or ethylene glycol monobutyl ether.

[0026] Preferably, the initiator includes at least one of azo initiators, peroxide initiators, or redox initiators.

[0027] More preferably, the initiator includes azo initiators, peroxide initiators, or combinations thereof.

[0028] More preferably, the initiator includes azobisisobutyronitrile, benzoyl peroxide, or a combination thereof.

[0029] Preferably, the acrylic resin is 5-12% by mass in the raw materials for preparing the acrylic-modified polyester resin; more preferably, it is 7-11%.

[0030] Preferably, the polyol includes at least one of neopentyl glycol, 1,3-propanediol, 1,4-cyclohexanediol or 2-ethyl-2-butyl-1,3-propanediol.

[0031] More preferably, the polyol is selected from one of the following combinations: 1) by mass parts 75-100 parts neopentyl glycol, 1-10 parts 1,3-propanediol, 1-10 parts 1,4-cyclohexanediol and 1-10 parts 2-ethyl-2-butyl-1,3-propanediol; or 2) by mass parts 85-100 parts neopentyl glycol, 1-10 parts 1,3-propanediol and 1-10 parts 1,4-cyclohexanediol.

[0032] Preferably, the polybasic acid includes at least one of isophthalic acid, 1,4-cyclohexanedicarboxylic acid, or hexahydrophthalic anhydride.

[0033] More preferably, the polybasic acid is selected from one of the following combinations: 1) 75-100 parts by mass of isophthalic acid, 1-10 parts by mass of 1,4-cyclohexanedicarboxylic acid and 1-10 parts by mass of hexahydrophthalic anhydride; or 2) isophthalic acid.

[0034] Preferably, the acid hydrolysate includes at least one of isophthalic acid, 1,4-cyclohexanedicarboxylic acid, or hexahydrophthalic anhydride.

[0035] More preferably, the acid hydrolysant is selected from one of the following combinations: 1) 75-100 parts by mass of isophthalic acid and 1-10 parts by mass of 1,4-cyclohexanedicarboxylic acid; or 2) 75-100 parts by mass of isophthalic acid and 5-20 parts by mass of hexahydrophthalic anhydride; or 3) isophthalic acid.

[0036] By further selecting the polyols, polyacids, or acid hydrolysants mentioned above, the resulting acrylic-modified polyester resin can have good mechanical properties, water resistance, and weather resistance, and the resulting powder coating can have a good appearance and gloss after coating is formed.

[0037] Preferably, the esterification catalyst includes at least one of tin-based catalysts, germanium-based catalysts, or titanium-based catalysts.

[0038] More preferably, the esterification catalyst is selected from tin-based catalysts.

[0039] More preferably, the esterification catalyst is selected from monobutyltin oxide.

[0040] Preferably, the acid value of the acrylic-modified polyester resin is 25~40 mgKOH / g; more preferably, it is 32~38 mgKOH / g.

[0041] Preferably, the hydroxyl value of the acrylic-modified polyester resin is <5 mgKOH / g.

[0042] Preferably, the melt viscosity of the acrylic-modified polyester resin at 200°C is 3000~6000 mPa·s; more preferably, it is 3500~4000 mPa·s.

[0043] Preferably, the glass transition temperature of the acrylic-modified polyester resin is 60~65℃; more preferably 62~63℃.

[0044] Preferably, the acrylic resin is prepared by a method comprising the following steps: mixing the raw materials for preparing the acrylic resin, and then performing a polymerization reaction to obtain the acrylic resin.

[0045] Preferably, in the preparation method of the acrylic resin, the polymerization reaction temperature is 50~180℃; more preferably 70~150℃.

[0046] A second aspect of the present invention provides a method for preparing an acrylic-modified polyester resin as described in the first aspect of the present invention, comprising the following steps: heating and melting a polyol in a protective gas atmosphere, adding a polyacid, an acrylic resin and an esterification catalyst to carry out an esterification reaction; adding an acidolytic agent to carry out an acidolytic reaction; and then carrying out a polycondensation reaction to obtain the acrylic-modified polyester resin.

[0047] Preferably, the esterification reaction is carried out sequentially in the following stages: a first stage esterification reaction, a second stage esterification reaction, a third stage esterification reaction, and a fourth stage esterification reaction; the holding temperature for the first stage esterification reaction is 175~185℃; the holding temperature for the second stage esterification reaction is 195~205℃; the holding temperature for the third stage esterification reaction is 215~225℃; and the holding temperature for the fourth stage esterification reaction is 230~240℃.

[0048] More preferably, the holding time for the first stage esterification reaction is 0.5~2h; the holding time for the second stage esterification reaction is 0.5~2h; the holding time for the third stage esterification reaction is 0.5~2h; and the holding time for the fourth stage esterification reaction is 2~4h.

[0049] More preferably, the heating rate of the first stage esterification reaction is 10~60℃ / h; the heating rate of the second stage esterification reaction is 10~30℃ / h; the heating rate of the third stage esterification reaction is 10~30℃ / h; and the heating rate of the fourth stage esterification reaction is 5~20℃ / h.

[0050] Preferably, the reaction temperature of the acidolysis reaction is 210~240℃; more preferably, it is 220~230℃.

[0051] Preferably, the acidolysis reaction proceeds until the acid value of the system is 40~50 mgKOH / g.

[0052] Preferably, the polycondensation reaction is carried out under vacuum conditions; the vacuum degree of the vacuum conditions is ≤ -0.09MPa.

[0053] Preferably, the polycondensation reaction proceeds until the acid value of the system is 25-40 mg KOH / g; more preferably, it is 32-38 mg KOH / g.

[0054] A third aspect of the present invention provides a powder coating comprising the following components: the acrylic-modified polyester resin described in the first aspect of the present invention, a curing agent, pigments, fillers, and additives.

[0055] Preferably, the curing agent includes at least one of isocyanate curing agents, amine curing agents, or acid anhydride curing agents; more preferably, the curing agent is selected from isocyanate curing agents; specifically, the isocyanate curing agent may include triglycidyl isocyanate (TGIC), diisocyanate, or a combination thereof; more preferably, the curing agent is selected from triglycidyl isocyanate (TGIC).

[0056] Preferably, the mass ratio of the acrylic modified polyester resin to the curing agent is 1:(0.3~1.5); more preferably 1:(0.5~1); and even more preferably 1:(0.7~0.8).

[0057] Preferably, the pigments and fillers include barium sulfate, titanium dioxide, or a combination thereof; more preferably, the pigments and fillers are selected from barium sulfate, and more specifically, precipitated barium sulfate.

[0058] Preferably, the additives include at least one of benzoin, leveling agent, or brightening agent; more preferably, the additives include benzoin, leveling agent, and brightening agent.

[0059] Preferably, the powder coating comprises the following components in parts by weight: 200-400 parts of the polyester resin described in the first aspect of the present invention, 10-40 parts of curing agent, 150-250 parts of pigments and fillers, and 2-20 parts of additives.

[0060] More preferably, the powder coating comprises the following components in parts by weight: 200-400 parts of the polyester resin described in the first aspect of the present invention, 10-40 parts of curing agent, 150-250 parts of barium sulfate, 0.5-5 parts of benzoin, 1-10 parts of leveling agent and 0.5-5 parts of gloss enhancer.

[0061] Preferably, the powder coating is prepared by a method comprising the following steps: mixing the components, melt extruding, flake forming, and crushing to obtain the powder coating.

[0062] A fourth aspect of the invention provides a coating formed from a powder coating comprising the powder coating described in the third aspect of the invention.

[0063] Preferably, the average thickness of the coating is 50~100μm; more preferably 60~80μm.

[0064] The fifth aspect of the present invention provides the application of a polyester resin as described in the first aspect of the present invention, or a powder coating as described in the third aspect of the present invention, or a coating as described in the fourth aspect of the present invention, in industrial roll protection, automotive parts protection, or waterproof material protection.

[0065] The beneficial effects of this invention are: by controlling the specific raw material composition of acrylic resin, the resulting polyacrylic resin has good weather resistance and better compatibility with polyester resin; by using this acrylic resin to modify polyester resin and introducing acrylic resin with carbon-carbon single bonds as the main chain, it can have excellent weather resistance while having good compatibility with conventional polyester resin, so that the final acrylic-modified polyester resin can be produced and coated on the same production line as existing polyester resin. Detailed Implementation

[0066] The following specific embodiments further illustrate the content of the present invention in detail. It should also be understood that the following embodiments are only for further explanation of the present invention and should not be construed as limiting the scope of protection of the present invention. Non-essential improvements and adjustments made by those skilled in the art based on the principles described herein are all within the scope of protection of the present invention. The specific process parameters, etc., in the following examples are merely examples within a suitable range; that is, those skilled in the art can make selections within a suitable range based on the description herein, and are not intended to be limited to the specific data in the examples below. Unless otherwise specified, the raw materials, reagents, or apparatus used in the following embodiments and comparative examples can be obtained from conventional commercial sources or by existing known methods.

[0067] Preparation Examples 1-4 and Preparation Comparative Example 1 Preparation Examples 1-4 and Comparative Example 1 provided a series of acrylic resins, referred to as acrylic resins 1-5, respectively. The raw materials and amounts used are shown in Table 1.

[0068] Table 1. Raw materials and amounts used in Preparation Examples 1-4 and Comparative Example 1 (amounts in g).

[0069] The preparation steps of the acrylic resin in Example 1 are as follows: In a reaction vessel, according to the proportions in Table 1 for Preparation Example 1, hard monomers, soft monomers, reactive monomers, and initiators were uniformly mixed and transferred to a constant-pressure dropping funnel. Solvent was added to a glass flask equipped with a thermometer, stirring paddle, reflux condenser, nitrogen tube, and constant-pressure dropping funnel. The mixture was heated to 70°C and maintained at this temperature, with nitrogen purging. The monomer mixture in the constant-pressure dropping funnel was then dripped into the glass flask. After the addition was completed within 4 hours, the mixture was kept at this temperature for 2 hours, then heated to 200°C and distilled under reduced pressure at a vacuum of -0.092 MPa. After 2 hours, the vacuum was released, and the mixture was cooled and discharged to obtain acrylic resin 1.

[0070] The preparation steps of the acrylic resin in Example 2 are as follows: In a reaction vessel, according to the proportions in Table 1 for Preparation Example 2, hard monomers, soft monomers, reactive monomers, and initiators were uniformly mixed and transferred to a constant-pressure dropping funnel. Solvent was added to a glass flask equipped with a thermometer, stirring paddle, reflux condenser, nitrogen tube, and constant-pressure dropping funnel. The mixture was heated to 100°C and held at this temperature, with nitrogen purging. The monomer mixture in the constant-pressure dropping funnel was then dripped into the glass flask. After the addition was completed within 3 hours, the mixture was held at this temperature for 2 hours, then heated to 200°C and distilled under reduced pressure at a vacuum of -0.092 MPa. After 2 hours, the vacuum was released, and the mixture was cooled and discharged to obtain acrylic resin 2.

[0071] The preparation steps of the acrylic resin in Example 3 are as follows: In a reaction vessel, according to the proportions in Table 1 for Preparation Example 3, hard monomers, soft monomers, and reactive monomers were uniformly mixed and transferred to a constant-pressure dropping funnel. Solvent was added to a glass flask equipped with a thermometer, stirring paddle, reflux condenser, nitrogen tube, and constant-pressure dropping funnel. The mixture was heated to 150°C and held at this temperature, with nitrogen purging. The monomer mixture from the constant-pressure dropping funnel was then dripped into the glass flask. After the addition was completed within 3 hours, the mixture was held at this temperature for 2 hours, then heated to 200°C and distilled under reduced pressure at a vacuum of -0.092 MPa. After 2 hours, the vacuum was released, and the mixture was cooled and discharged to obtain acrylic resin 3.

[0072] The preparation steps of the acrylic resin in Example 4 are as follows: In a reaction vessel, according to the proportions in Example 4 of Table 1, hard monomers, soft monomers, reactive monomers, and initiators were uniformly mixed and transferred to a constant-pressure dropping funnel. Solvent was added to a glass flask equipped with a thermometer, stirring paddle, reflux condenser, nitrogen tube, and constant-pressure dropping funnel. The mixture was heated to 70°C and held at this temperature, with nitrogen purging. The monomer mixture in the constant-pressure dropping funnel was then dripped into the glass flask. After the addition was completed within 4 hours, the mixture was held at this temperature for 2 hours, then heated to 200°C and distilled under reduced pressure at a vacuum of -0.092 MPa. After 2 hours, the vacuum was released, and the mixture was cooled and discharged to obtain acrylic resin 4.

[0073] The preparation steps for the acrylic resin in Comparative Example 1 are as follows: Prepare the mixture of hard monomers, soft monomers, reactive monomers, and initiator in a reaction vessel according to the proportions in Table 1 for Comparative Example 1, and transfer the mixture to a constant-pressure dropping funnel. Add solvent to a glass flask equipped with a thermometer, stirring paddle, reflux condenser, nitrogen tube, and constant-pressure dropping funnel, heat to 70°C and maintain the temperature, purge with nitrogen, and drip the monomer mixture from the constant-pressure dropping funnel into the glass flask. After the addition is completed within 4 hours, maintain the temperature for 2 hours, then raise the temperature to 200°C and distill under reduced pressure at a vacuum of -0.092 MPa. After 2 hours, release the vacuum and cool down to obtain acrylic resin 5.

[0074] Resin Examples 1-4 and Resin Comparative Example 1 Examples 1-4 and Comparative Example 1 provide a series of acrylic-modified polyester resins, using the acrylic resins from Examples 1-4 and Comparative Example 1 as raw materials. The specific raw materials and amounts are shown in Table 2.

[0075] Table 2. Raw materials and amounts used in the preparation of resins in Examples 1-4 and Comparative Example 1 (amounts are in g).

[0076] The preparation steps of the acrylic-modified polyester resin in Resin Example 1 are as follows: In a reactor, according to the resin formulation in Example 1 of Table 2, the polyol was heated until the material melted, and polyacid, acrylic resin and esterification catalyst were added. Nitrogen gas was introduced, and the temperature was raised to 160°C within 3 hours, then raised to 180°C within 1 hour and held for 1 hour, then raised to 200°C within 1 hour and held for 1 hour, then raised to 220°C within 1 hour and held for 1 hour, and finally raised to 230-240°C within 2 hours and held for 3 hours to obtain the esterified product. Under nitrogen purging, the temperature was lowered to 230℃, and an acid hydrolysate was added to the esterification product. The acid hydrolysis reaction was carried out for 3 hours to obtain the acid hydrolysis product with an acid value of 40-50 mg KOH / g. Subsequently, a vacuum polycondensation reaction was carried out at a vacuum degree of -0.092 MPa for 3 hours. The acid value was about 25 mg KOH / g, the hydroxyl value was less than 5 mg KOH / g, and the melt viscosity at 200℃ was 5000-6000 mPa.s. The temperature was lowered to 195-205℃ to obtain acrylic modified polyester resin 1 with a glass transition temperature of 61.33℃ and a reactivity of 330s.

[0077] The preparation steps of the acrylic-modified polyester resin in Resin Example 2 are as follows: In a reactor, according to the resin ratio in Example 2 of Table 2, the polyol was heated until the material melted, and the polyacid, acrylic resin and esterification catalyst were added. Nitrogen gas was introduced, and the temperature was raised to 160°C within 3 hours, then raised to 180°C within 1 hour and held for 1 hour, then raised to 200°C within 1 hour and held for 1 hour, then raised to 220°C within 1 hour and held for 1 hour, and finally raised to 230-240°C within 2 hours and held for 3 hours to obtain the esterified product. Under nitrogen purging, the temperature was lowered to 220℃, and an acid hydrolysate was added to the esterification product. The acid hydrolysis reaction was carried out for 3 hours to obtain the acid hydrolysis product with an acid value of 40-50 mg KOH / g. Subsequently, a vacuum polycondensation reaction was carried out at a vacuum degree of -0.092 MPa for 3 hours. The acid value was about 30 mg KOH / g, the hydroxyl value was less than 5 mg KOH / g, and the melt viscosity at 200℃ was 4000-5000 mPa.s. The temperature was lowered to 195-205℃ to obtain acrylic modified polyester resin 2 with a glass transition temperature of 64.45℃ and a reactivity of 260s.

[0078] The preparation steps of the acrylic-modified polyester resin in Resin Example 3 are as follows: In a reactor, according to the resin ratio in Example 3 of Table 2, the polyol was heated until the material melted, and the polyacid, acrylic resin and esterification catalyst were added. Nitrogen gas was introduced, and the temperature was raised to 160°C within 3 hours, then raised to 180°C within 1 hour and held for 1 hour, then raised to 200°C within 1 hour and held for 1 hour, then raised to 220°C within 1 hour and held for 1 hour, and finally raised to 230-240°C within 2 hours and held for 3 hours to obtain the esterified product. Under nitrogen purging, the temperature was lowered to 230℃, and an acid hydrolysate was added to the esterification product. The acid hydrolysis reaction was carried out for 5 hours to obtain the acid hydrolysis product with an acid value of 40-50 mg KOH / g. Subsequently, a vacuum polycondensation reaction was carried out at a vacuum degree of -0.092 MPa for 3 hours. The acid value was about 35 mg KOH / g, the hydroxyl value was less than 5 mg KOH / g, and the melt viscosity at 200℃ was 3500-4000 mPa.s. The temperature was lowered to 195-205℃ to obtain acrylic modified polyester resin 3 with a glass transition temperature of 62.81℃ and a reactivity of 245s.

[0079] The preparation steps of the acrylic-modified polyester resin in Resin Example 4 are as follows: In a reactor, according to the resin formulation in Example 4 of Table 2, the polyol was heated until the material melted, and polyacid, acrylic resin and esterification catalyst were added. Nitrogen gas was introduced, and the temperature was raised to 160°C within 3 hours, then raised to 180°C within 1 hour and held for 1 hour, then raised to 200°C within 1 hour and held for 1 hour, then raised to 220°C within 1 hour and held for 1 hour, and finally raised to 230-240°C within 2 hours and held for 3 hours to obtain the esterified product. Under nitrogen purging, the temperature was lowered to 225℃, and an acid hydrolysate was added to the esterification product. The acid hydrolysis reaction was carried out for 6 hours to obtain the acid hydrolysis product with an acid value of 40-50 mg KOH / g. Subsequently, a vacuum polycondensation reaction was carried out at a vacuum degree of -0.092 MPa for 6 hours. The acid value was about 40 mg KOH / g, the hydroxyl value was less than 3 mg KOH / g, and the melt viscosity at 200℃ was 3000-3500 mPa.s. The temperature was lowered to 195-205℃ to obtain acrylic modified polyester resin 4 with a glass transition temperature of 61.42℃ and a reactivity of 170s.

[0080] The preparation steps of the acrylic-modified polyester resin in Comparative Example 1 are as follows: In a reactor, according to the resin ratio in Table 2 (Example 1), the polyol is heated until the material melts, and polyacid, acrylic resin and esterification catalyst are added. Nitrogen gas is introduced, and the temperature is raised to 160°C within 3 hours, then raised to 180°C within 1 hour and held for 1 hour, then raised to 200°C within 1 hour and held for 1 hour, then raised to 220°C within 1 hour and held for 1 hour, and finally raised to 230-240°C within 2 hours and held for 3 hours to obtain the esterified product. Under nitrogen purging, the temperature was lowered to 225℃, and an acid hydrolysate was added to the esterification product. The acid hydrolysis reaction was carried out for 6 hours to obtain the acid hydrolysis product with an acid value of 40-50 mg KOH / g. Subsequently, a vacuum polycondensation reaction was carried out at a vacuum degree of -0.092 MPa for 6 hours. The acid value was about 45 mg KOH / g, the hydroxyl value was less than 3 mg KOH / g, and the melt viscosity at 200℃ was 3000-3500 mPa.s. The temperature was lowered to 195-205℃ to obtain acrylic modified polyester resin 5 with a glass transition temperature of 61.42℃ and a reactivity of 125s.

[0081] Resin Comparative Example 2 A commercially available conventional ultra-weather-resistant polyester resin has an acid value of 30~36 mgKOH / g, a hydroxyl value of less than 5 mgKOH / g, a melt viscosity of 5000~6000 mPa·s at 200℃, a glass transition temperature of 64~66℃, and a reactivity of 120~240s.

[0082] The properties of the polyester resins obtained in Examples 1-4 and Comparative Examples 1-2 are shown in the table below. The acid value was tested according to GB / T 6743-2008; the hydroxyl value according to GB / T 12008.3-2009; the melt viscosity at 200℃ according to GB / T 27808-2011; the glass transition temperature according to ISO 11357-2:2020; and the reactivity according to Q / QTCL1-2014.

[0083] Table 3. Properties of the polyester resins in Resin Examples 1-4 and Resin Comparative Examples 1-2

[0084] Coating Examples 1-4 and Coating Comparative Examples 1-2 Examples 1-4 and Comparative Examples 1-2 of the coatings provided a series of powder coatings, which used the polyester resins from Examples 1-4 and Comparative Examples 1-2 of the resins as the raw materials. The specific components and amounts are shown in Table 4. Among them, the precipitated barium sulfate was purchased from Guangxi Lianzhuang Technology Co., Ltd., under the Xiangxing brand.

[0085] Table 4. Components and dosages of powder coatings in Examples 1-4 and Comparative Examples 1-2 (dosage unit: g).

[0086] The preparation methods of the powder coatings in Examples 1-4 and Comparative Examples 1-2 are as follows: Weigh each component according to Table 4, mix them evenly, melt and extrude them using a screw extruder, press them into sheets, crush them, and then pulverize and sieve the sheets to obtain the powder coatings.

[0087] Performance testing The powder coatings from the above coating examples and comparative examples were electrostatically sprayed onto degreased and derusted iron plates, baked at 200°C for 10 minutes, and the coating thickness was 60~80μm. The following performance tests were then conducted: (1) Gloss shall be tested in accordance with GB / T 9754-2007; (2) Impact resistance is tested according to GB / T 1732-2020. The weight of the hammer is 1000±1g and the height of the hammer is 50.0±0.1cm. If no cracks, wrinkles and peeling are observed, it is considered to pass; otherwise, it is considered to fail. (3) Water resistance shall be determined according to GB / T 1733-1993 (immersion in boiling water test method), boiled in water for 2 hours, with gloss retention rate as the evaluation standard; (4) Weather resistance shall be determined in accordance with GB / T 1865-2009, UVB, for 480h, with gloss retention rate as the evaluation standard; (5) Co-production and coating compatibility test of resins: The laboratory used various acrylic modified polyester resins and commercially available conventional ultra-weather resistant polyester resins in a specific order. They were weighed and mixed with curing agent TGIC, leveling agent GLP588, precipitated barium sulfate, benzoin and brightening agent 701 according to the proportions in Table 4 above and then mixed to prepare powder coatings. The prepared powder coatings were electrostatically sprayed onto degreased and derusted iron plates and baked at 200℃ for 10 min. The coating thickness was 60~80μm. After the above simulated co-production and coating compatibility test was conducted 5 times, the coating was observed to see if there were defects such as pinholes, fish eyes and decreased leveling. If there were no defects, it indicated that the compatibility was good.

[0088] The performance test results are shown in Table 5.

[0089] Table 5 Performance test results of powder coatings in Examples 1-4 and Comparative Examples 1-2

[0090] As shown in Table 5, the powder coatings prepared using the acrylic-modified polyester resins of the various resin examples of this invention exhibit good water resistance and weather resistance, and demonstrate good compatibility with commercially available conventional ultra-weather-resistant polyester resins. They can be produced and coated on the same production line as polyester resins, and no product defects were found during the process. Specifically, compared to commercially available conventional ultra-weather-resistant polyester resins, the powder coating prepared using the acrylic-modified polyester resin of Resin Example 3 of this invention not only has better water resistance and weather resistance, but also exhibits essentially the same appearance, gloss, and impact resistance as commercially available conventional ultra-weather-resistant polyester resins.

[0091] In this embodiment of the invention, an acrylic resin with excellent weather resistance and a carbon-carbon single bond main chain is introduced into the polyester resin structure. This makes the weather resistance of the acrylic modified polyester resin significantly better than that of commercially available conventional ultra-weather-resistant polyester resin. At the same time, this resin has good compatibility with commercially available conventional polyester resin and can be produced and coated on the same production line as conventional polyester resin.

[0092] The acrylic-modified polyester resin prepared in the embodiments of the present invention has acid value, hydroxyl value, melt viscosity, glass transition temperature, reactivity, and other indicators that meet the requirements for use in powder coatings. When prepared into powder coatings, it exhibits good water resistance and weather resistance, and can achieve good appearance, gloss, and impact resistance. The acrylic-modified polyester resin, powder coating, or coating provided in the embodiments of the present invention has good application prospects in industrial roll protection, automotive parts protection, or waterproof material protection.

[0093] In summary, this invention, by controlling the specific raw material composition of acrylic resin, produces a polyacrylic resin with good weather resistance and better compatibility with polyester resin. Furthermore, by modifying polyester resin with this acrylic resin and introducing acrylic resin with carbon-carbon single bonds as the main chain, it achieves excellent water-boiling resistance and weather resistance while maintaining good compatibility with conventional polyester resin. This allows the final acrylic-modified polyester resin to be produced and coated on the same production line as existing polyester resins.

Claims

1. An acrylic-modified polyester resin, characterized in that, The acrylic-modified polyester resin is prepared from the following raw materials in parts by weight: 31-40 parts polyol, 31-60 parts polyacid, 4-30 parts acrylic resin, 5-20 parts acid hydrolysate and 0.01-0.2 parts esterification catalyst; the acrylic resin accounts for 3-13% of the raw materials in the preparation of the acrylic-modified polyester resin by weight. The acrylic resin is prepared from the following raw materials in parts by weight: 40-70 parts hard monomer, 5-20 parts soft monomer, 5-15 parts reactive monomer, 18-50 parts solvent and 0-5 parts initiator; the reactive monomer is 6-12% by weight in the raw materials for preparing the acrylic resin; the reactive monomer includes at least one of methacrylic acid, acrylic acid, hydroxyethyl acrylate or glycidyl methacrylate.

2. The acrylic-modified polyester resin according to claim 1, characterized in that, The reactive monomer is selected from one of the following combinations: 1) 10-25 parts by weight of methacrylic acid and 75-90 parts by weight of acrylic acid; or 2) hydroxyethyl acrylate; or 3) glycidyl methacrylate.

3. The acrylic-modified polyester resin according to claim 1, characterized in that, The hard monomer includes at least one of methyl methacrylate, methyl acrylate, styrene, or cyclohexyl methacrylate; And / or, the soft monomer includes at least one of n-butyl acrylate, n-hexyl acrylate, dodecyl acrylate, or lauryl acrylate; And / or, the solvent includes at least one of ethyl acetate, butyl acetate, n-butanol, xylene, propylene glycol methyl ether acetate, ethylene glycol monomethyl ether, or ethylene glycol monobutyl ether; And / or, the initiator includes at least one of azo initiators, peroxide initiators, or redox initiators; And / or, the polyol includes at least one of neopentyl glycol, 1,3-propanediol, 1,4-cyclohexanediol or 2-ethyl-2-butyl-1,3-propanediol; And / or, the polybasic acid includes at least one of isophthalic acid, 1,4-cyclohexanedicarboxylic acid or hexahydrophthalic anhydride; And / or, the acid hydrolysant includes at least one of isophthalic acid, 1,4-cyclohexanedicarboxylic acid, or hexahydrophthalic anhydride; And / or, the esterification catalyst includes at least one of tin-based catalysts, germanium-based catalysts, or titanium-based catalysts.

4. The acrylic-modified polyester resin according to claim 3, characterized in that, The hard monomer is selected from one of the following combinations: 1) 35-70 parts by weight of methyl methacrylate, 5-20 parts by weight of methyl acrylate and 5-2 parts by weight of cyclohexyl methacrylate; or 2) 35-70 parts by weight of methyl methacrylate, 5-20 parts by weight of methyl acrylate and 10-45 parts by weight of styrene. And / or, the soft monomer is selected from the following combination: 1 to 20 parts by weight of n-butyl acrylate, 1 to 10 parts by weight of n-hexyl acrylate and 75 to 100 parts by weight of lauryl acrylate; And / or, the polyol is selected from one of the following combinations: 1) 75-100 parts by weight of neopentyl glycol, 1-10 parts by weight of 1,3-propanediol, 1-10 parts by weight of 1,4-cyclohexanediol and 1-10 parts by weight of 2-ethyl-2-butyl-1,3-propanediol; or 2) 85-100 parts by weight of neopentyl glycol, 1-10 parts by weight of 1,3-propanediol and 1-10 parts by weight of 1,4-cyclohexanediol; And / or, the polyacid is selected from one of the following combinations: 1) 75 to 100 parts by mass of isophthalic acid, 1 to 10 parts by mass of 1,4-cyclohexanedicarboxylic acid and 1 to 10 parts by mass of hexahydrophthalic anhydride; or 2) isophthalic acid; And / or, the acid hydrolysant is selected from one of the following combinations: 1) 75-100 parts by weight of isophthalic acid and 1-10 parts by weight of 1,4-cyclohexanedicarboxylic acid; or 2) 75-100 parts by weight of isophthalic acid and 5-20 parts by weight of hexahydrophthalic anhydride; or 3) isophthalic acid.

5. The acrylic-modified polyester resin according to claim 1, characterized in that, The acid value of the acrylic-modified polyester resin is 25~40 mgKOH / g; And / or, the hydroxyl value of the acrylic-modified polyester resin is <5 mg KOH / g; And / or, the melt viscosity of the acrylic-modified polyester resin at 200°C is 3000~6000 mPa·s; And / or, the glass transition temperature of the acrylic-modified polyester resin is 60~65℃.

6. A method for preparing an acrylic-modified polyester resin as described in any one of claims 1 to 5, characterized in that, Includes the following steps: In a protective gas atmosphere, a polyol is heated and melted, and polyacids, acrylic resins, and esterification catalysts are added to carry out an esterification reaction; an acid hydrolysis agent is added to carry out an acid hydrolysis reaction; then a polycondensation reaction is carried out to obtain the acrylic modified polyester resin.

7. The preparation method according to claim 6, characterized in that, The esterification reaction is carried out sequentially in four stages: a first stage esterification reaction, a second stage esterification reaction, a third stage esterification reaction, and a fourth stage esterification reaction. The holding temperature for the first stage esterification reaction is 175~185℃; the holding temperature for the second stage esterification reaction is 195~205℃; the holding temperature for the third stage esterification reaction is 215~225℃; and the holding temperature for the fourth stage esterification reaction is 230~240℃. And / or, the reaction temperature of the acidolysis reaction is 220~230℃; And / or, the polycondensation reaction is carried out under vacuum conditions; the vacuum degree of the vacuum conditions is ≤ -0.09 MPa.

8. A powder coating, characterized in that, The powder coating comprises the following components: acrylic-modified polyester resin according to any one of claims 1 to 5, curing agent, pigments, fillers and additives.

9. A coating, characterized in that, The coating is formed from a powder coating as described in claim 8; The average thickness of the coating is 50~100μm.

10. The application of an acrylic-modified polyester resin as described in any one of claims 1 to 5, or a powder coating as described in claim 8, or a coating as described in claim 9, in industrial roll protection, automotive parts protection, or waterproof material protection.

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